A class diesel - blackish exhaust emission

[mercyme]

Hi,everyone,
Had maf sensor replaced 4000 miles ago as kickdown wasn't operating.
Ever since, have had a film of blackish smoke coming out, only in motion,not when still.
Nothing wrong with performance,mpg very good, no strange engine noises.
Smoke bit thicker for 2 or 3 seconds, when kickdown to accelerate quickly on the odd occasion.
Have taken back to Merc twice, say they can't notice anything.
Have written to Merc HQ, who are looking into my complaint.
Has anybody any words of wisdom,please?

 

[mercyme]

Is there nobody out there with any advice

 

[SilverSaloon]

Is there nobody out there with any advice

you need to give it a little more time!!! someone will be along with some advice soon enough!!

some more info on the year of the A class and the specific engine fitted would help

 

[mercyme]

a class

Car is 170 CDi auto 2002
A businessman followed me in his Merc and asked if I was using a lot of fuel, that's the point, no less than before this problem.

 

[Dieselman]

The new MAF is causing it to fuel up more on demand so you notice more smoke but it could have a problem with poor injectors spray pattern or a sticky EGR valve.

Try cleaning out the EGR valve and a strong dose of injector cleaner to see if there is any change.

Next up would be looking for lost boost due to leaking intake pipes.

 

[mercyme]

Following on, Merc dealer advised by Head office to have my car back in.
Finally agreed that,yes there is blackish smoke being emitted, however weren't able to give diagnosis, but if they could have the car in for a day or two, to strip down.
Are they having a laugh or what?

 

[renault12ts]

Try Millers DPS4 . There are plenty of threads on here about it.

 

[hawk20]

A small puff of smoke when you kick-down, on a 7 year old car, is not something that I would worry about. Keep on trucking and if there is something wrong it will eventually show up with stronger symptoms.

 

[BlackC55]

They do tend to smoke a bit when pushed hard.

 

[mercyme]

Hi, I appreciate what you're all saying, but even though it's not noticable from inside the car, it is noticable how a lot of traffic backs off when following. Also,what at MOT time?

 

[BlackC55]

Use some injector cleaner and then go for a good blast at full throttle and high RPM and this should help give a good clearout.

 

[renault12ts]

Use some injector cleaner and then go for a good blast at full throttle and high RPM and this should help give a good clearout.

I agree. Or start with Miller DPS4, as I said earlier.

 

[mercyme]

Hi,I take what you're saying,but apart from"small puff of smoke"there is a film of black smoke, all the time the car is in motion. With regards to cleaners it has had that since the problem started. Please don't say the car must be f****d, because it does perform ok. Thanks for advice.

 

[mercyme]

Well I tried Millers, and hasn't made any difference.
Ain't there nobody else out there who's heard of these symptoms before.

 

[wemorgan]

Finally agreed that,yes there is blackish smoke being emitted, however weren't able to give diagnosis, but if they could have the car in for a day or two, to strip down.

Are they offering to do this for free or at cost?

Is the engine burning any oil?

 

[mercyme]

Mercedes do for free, Yea right. I wish.

Apart from black smoke, everything is what it should be.
No oil loss, over 9miles to litre, diesel.

 

[wemorgan]

What part of the country are you from?
Maybe someone can recommend a local independent garage for you.

 

[hawk20]

Mercedes do for free, Yea right. I wish.

Apart from black smoke, everything is what it should be.
No oil loss, over 9miles to litre, diesel.

Do you mean 9,000 miles to the litre. If so just drive it and stop worrying. A puff of smoke when you kick down is not something I would worry about. And if it is something more serious the toothache will get worse.

 

[mercyme]

With respect Hawk, it is film of black smoke all the time the car is in motion, plus cloud at kickdown.
Wouldn't 9000 miles to litre be just great,less than a fiver a year on diesel.

 

[wemorgan]

Crossed wires I think.......

I suspect hawk20 was talking about oil consumption, whilst you're talking about fuel?

In which case are you using fuel at 9 miles per litre = 40 mpg?
That does sound rather low to me.

edit: If the problem came exactly after the new MAF have you tried unplugging it to see if there is any difference?